Re: AO40: status

On Sun, 7 Jan 2001, Richard D. Burgan wrote:
> Bob,
> AO-40's spin rate rate went from about 9 prior to loss of comm to 17+ after
> comm was regained. These are based on telemetry and doppler measurement
> respectively.
> 73's Rich @ WC8J
Wow, thanks rick. That is a very perfect match to the theory of simple
spin up due to the loss of 250 Kg of mass from a 500 Kg spacecraft.
ALthough it is hard to believe that all three "fuels" and "gasses" all
were lost in one event... Hummh... And if both the oxidizer and fuel
both went at the same time there would be a real mess...
Thanks
Bob
>
> Bob Bruninga wrote:
>
> > On Sat, 6 Jan 2001, Phil Karn wrote:
> >
> > > Nope, not quite. If the fuel had simply dribbled out from the outer
> > > edges of the spacecraft, the spin would have slowed down as the
> > > propellant moved outward.
> >
> > Yep, in this case, I was taking your assumption of it leaking off near
> > the center. Thus it does not take away any angular momentum and the
> > spaceframe must spin up to conserve the angular momentum... But even if it
> > moved outwards, it didn't stay there but just left the spinning
> > system without taking away any angular momentum. Thus, in any case, it
> > must spin faster...
> >
> > > > >How much was the mass of the propellant? >
> > > The figures I have show 63.37 kg of N2O4 in each of two tanks, 34.35 kg
> > > of MMH in each of two tanks, plus 26.65 kg of NH3 in each of two tanks.
> > > I can't find a figure for the helium mass.
> >
> > Wow, my 250 Kg wild a$$ guess was pretty close. So that sould explain a
> > doubling of the spin of a 500 Kg spacecraft. Its about 18 now, did I hear
> > someone say it was about 6 at the start of the burn? That leaves the last
> > 6 RPM to be accounted for by the reaction of uneaven tangential
> > venting? Seems plausible...
> >
> > de WB4APR, BOb
> >
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>
>
de WB4APR@amsat.org, Bob
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